It is your responsibility to monitor the client account balances regularly and to ensure funds are only held in relation to the underlying transaction and, if they are no longer required, that they are returned promptly to the client. You can easily review client balances by viewing the relevant matter in Keyed-In or alternatively by running a matter balance report from within Keyed-In (Financials/Keystone Financials/Reports/Matter Balance Report).
When the matter completes, as part of file closure, you will need to ensure any residual client balances are returned to the client.